audio: Fix output blocking condition in the remote submix

During transition to AIDL, the condition for blocking writes
on the output stream of the remote submix was not transferred
correctly. This logic was fixed.

While testing the fixed logic, some deficiencies in the VTS
tests were found and also fixed.

Bug: 383982254
Test: atest --test-filter="AudioModuleRemoteSubmix*" VtsHalAudioCoreTargetTest
Change-Id: Iecd5ecd329d61764b314744eaf4afb6196a38e3e